WELCOME BACK, SENIORS - On the first day of their senior year, Elena (Nina Dobrev), Caroline (Candice Accola), Bonnie (Kat Graham) and Matt (Zach Roerig) are still reeling from recent events, while Tyler (Michael Trevino) seems to be enjoying everything a little too much. Damon (Ian Somerhalder) is annoyed by a new houseguest, and everyone is surprised by the arrival of a new student in Alaric's (Matt Davis) history class. Matt asks Bonnie for help when he realizes he made a serious mistake. Meanwhile, Stefan (Paul Wesley) continues to carry out his latest assignment from Klaus (Joseph Morgan, who does not appear in the episode).